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Room-temperature operation of near-infrared light-emitting diode based on Tm-doped GaN with ultra-stable emission wavelength
摘要： Near-infrared (NIR) light with a wavelength of 650–950 nm is used for various biomedical applications. Although NIR emitters are typically based on GaAs-related materials, they contain toxic elements, and the emission wavelength can easily shift during the device operation due to temperature changes and current injection levels. On the other hand, Tm3t, which is one of the rare-earth ions, can generate ultra-stable NIR luminescence with a wavelength of (cid:1)800 nm, based on 3H4 – 3H6 transitions in a 4f shell, and we have recently focused on Tm-doped GaN (GaN:Tm) based light-emitting diodes (LEDs) as novel NIR emitters. In this paper, we present a demonstration of a NIR-LED based on GaN:Tm grown by the organometallic vapor phase epitaxy method with optimized growth conditions and structures, where the parasitic reaction is well suppressed. NIR luminescence from the GaN:Tm-based LED is derived from 3H4 – 3H6 transitions of Tm3t ions and consists of three dominant peaks at 795, 806, and 814 nm. The turn-on voltage of the NIR-LED is (cid:1)6:9 V, and it is significantly lower than the previously reported electroluminescent devices based on GaN:Tm with impact ionization processes. From a current dependence of the electroluminescence spectra and temperature-dependent photoluminescence for the NIR-LED, the peak shifts are determined to be ,7:6 pm/mA and (cid:1)1:3 pm/K, respectively.
关键词： Tm-doped GaN,ultra-stable emission wavelength,Near-infrared,organometallic vapor phase epitaxy,light-emitting diode
更新于2025-09-23 15:19:57
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Optical Fiber Applications || All Optical Signal Processing Technologies in Optical Fiber Communication
摘要： Due to continued growth of internet at starling rate and the introduction of new broadband services, such as cloud computing, IPTV and high-definition media streaming, there is a requirement for flexible bandwidth infrastructure that supports mobility of data at peta-scale. Elastic networking based on gridless spectrum technology is evolving as a favorable solution for the flexible optical networking supportive next generation traffic requirements. Recently, research is centered on a more elastic spectrum provision methodology than the traditional ITU-T grid. The main issue is the requirement for a transmission connect, capable of accommodating and handling a variety of signals with distinct modulation format, baud rate and spectral occupancy. Segmented use of the spectrum could lead to the shortage of availableness of sufficiently extensive spectrum spaces for high bitrate channels, resulting in wavelength contention. On-demand space assignment creates not only deviation from the ideal course but also have spectrum fragmentation, which reduces spectrum resource utilization. This chapter reviewed the recent research development of feasible solutions for the efficient transport of heterogeneous traffic by enhancing the flexibility of the optical layer for performing allocation of network resources as well as implementation of optical node by all optical signal processing in optical fiber communication.
关键词： wavelength conversion,defragmentation,semiconductor optical amplifier,multicasting,format conversion,grooming,optical signal processing
更新于2025-09-23 15:19:57
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Towards visible-wavelength passively mode-locked lasers in all-fibre format
摘要： Mode-locked fibre lasers (MLFLs) are fundamental building blocks of many photonic systems used in industrial, scientific and biomedical applications. To date, 1–2 μm MLFLs have been well developed; however, passively mode-locked fibre lasers in the visible region (380–760 nm) have never been reported. Here, we address this challenge by demonstrating an all-fibre visible-wavelength passively mode-locked picosecond laser at 635 nm. The 635 nm mode-locked laser with an all-fibre figure-eight cavity uses a Pr/Yb codoped ZBLAN fibre as the visible gain medium and a nonlinear amplifying loop mirror as the mode-locking element. First, we theoretically predict and analyse the formation and evolution of 635 nm mode-locked pulses in the dissipative soliton resonance (DSR) regime by solving the Ginzburg-Landau equation. Then, we experimentally demonstrate the stable generation of 635 nm DSR mode-locked pulses with a pulse duration as short as ~96 ps, a radio-frequency signal-to-noise ratio of 67 dB and a narrow spectral bandwidth of <0.1 nm. The experimental results are in excellent agreement with our numerical simulations. In addition, we also observe 635 nm noise-like pulse operation with a wide (>1 nm) and modulated optical spectrum. This work represents an important step towards miniaturized ultrafast fibre lasers in the visible spectral region.
关键词： visible-wavelength,mode-locked fibre lasers,all-fibre format,dissipative soliton resonance,passively mode-locked
更新于2025-09-23 15:19:57
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Nonlinear Optics in Dielectric Guided-Mode Resonant Structures and Resonant Metasurfaces
摘要： Nonlinear optics is an important area of photonics research for realizing active optical functionalities such as light emission, frequency conversion, and ultrafast optical switching for applications in optical communication, material processing, precision measurements, spectroscopic sensing and label-free biological imaging. An emerging topic in nonlinear optics research is to realize high efficiency optical functionalities in ultra-small, sub-wavelength length scale structures by leveraging interesting optical resonances in surface relief metasurfaces. Such artificial surfaces can be engineered to support high quality factor resonances for enhanced nonlinear optical interaction by leveraging interesting physical mechanisms. The aim of this review article is to give an overview of the emerging field of nonlinear optics in dielectric based sub-wavelength periodic structures to realize efficient harmonic generators, wavelength mixers, optical switches etc. Dielectric metasurfaces support the realization of high quality-factor resonances with electric field concentrated either inside or in the vicinity of the dielectric media, while at the same time operate at high optical intensities without damage. The periodic dielectric structures considered here are broadly classified into guided-mode resonant structures and resonant metasurfaces. The basic physical mechanisms behind guided-mode resonances, electromagnetically-induced transparency like resonances and bound-states in continuum resonances in periodic photonic structures are discussed. Various nonlinear optical processes studied in such structures with example implementations are also reviewed. Finally, some future directions of interest in terms of realizing large-area metasurfaces, techniques for enhancing the efficiency of the nonlinear processes, heterogenous integration, and extension to non-conventional wavelength ranges in the ultra-violet and infrared region are discussed.
关键词： harmonic generation,guided-mode resonance,four-wave mixing,Mie scattering,optical resonances,nonlinear optics,sub-wavelength gratings,Fano resonances,optical switching
更新于2025-09-23 15:19:57
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Design of a Surface Plasmon Resonance-Enhanced ZnO Ultraviolet Photodetector Based on a Sub-wavelength Metal Grating Covered with a High-Refractive-Index Medium
摘要： To realize a surface plasmon resonance-enhanced zinc oxide (ZnO) ultraviolet photodetector based on a sub-wavelength metal grating, we take advantage of the sensitivity of the resonance condition of a sub-wavelength metal grating to the refractive index of the surrounding medium. We theoretically design a sub-wavelength Ag grating covered with a high-refractive-index medium layer and apply it to a ZnO ultraviolet photodetector. By optimizing the parameters (angle of incidence, grating period, grating spacing, grating thickness, high-refractive-index medium layer thickness, refractive index of the covering), the optical ?eld is localized at the interface of the sub-wavelength Ag grating and the ZnO thin ?lm; that is, surface plasmon resonance is realized within the device. Compared with the device without a high-refractive-index medium layer, the maximum absorption enhancement factor of the designed device can reach up to 108. This work will provide theoretical guidance to realize a surface plasmon resonance-enhanced ZnO ultraviolet photodetector with a sub-wavelength metal grating.
关键词： ultraviolet photodetector,ZnO,sub-wavelength metal grating,Surface plasmon resonance
更新于2025-09-23 15:19:57
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Temperature dependence of nonradiative recombination processes in UV-B AlGaN quantum well revealed by below-gap excitation light
摘要： Nonradiative recombination (NRR) processes through defect states and their temperature dependence in UV-B AlGaN MQW sample on sapphire substrate grown by MOCVD technique have been studied by photoluminescence (PL) spectroscopy. We detected NRR centers by adding a below-gap excitation light with photon energies from 0.93 eV to 1.46 eV on an above-gap excitation light of 4.66 eV. All the BGE energies decreased PL intensity at 25 K, and the most-distinct quenching is observed by 1.27 eV BGE at the same BGE photon number density. The temperature-dependent PL intensity for the BGE energy of 1.27 eV is interpreted by three NRR centers. The one-level model dominates over that of two-level model in the temperature range 58 K < T < 88 K. The two-level model prevails in other region of temperature. The combination of one-level and two-level models is consistent with the spectral peak-energy shift as a function of temperature.
关键词： AlGaN,Quantum well,Two-wavelength excited photoluminescence,Recombination model,Nonradiative recombination center
更新于2025-09-23 15:19:57
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[IEEE 2018 16th International Conference on Emerging eLearning Technologies and Applications (ICETA) - Stary Smokovec, Slovakia (2018.11.15-2018.11.16)] 2018 16th International Conference on Emerging eLearning Technologies and Applications (ICETA) - High-Capacity Wavelength Division Multiplexing Optical Transmission Systems
摘要： The new services and constantly growing number of users develop constant pressure for current transmission systems. Although the first optical systems started to be used at the beginning of 1980s, the last forty years have brought unprecedented development of these systems. Today's optical transmission systems play key role for satisfaction bandwidth demands. This paper provides short insight into the technological evolution of optical transmission systems and show why these systems are mostly used in long-haul and metro networks. The first transmission systems had transmission capacity around 45 Mb/s, today's capacity is beyond 2 Pb/s. We looked at the key technologies as well as their future trends.
关键词： optical transmission systems,wavelength division multiplexing,bandwidth demands,WDM,CWDM,DWDM,optical fiber
更新于2025-09-23 15:19:57
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[IEEE 2018 41st International Spring Seminar on Electronics Technology (ISSE) - Zlatibor, Serbia (2018.5.16-2018.5.20)] 2018 41st International Spring Seminar on Electronics Technology (ISSE) - Implementation of the Audio Signal Transmission System Using Wavelength Division Multiplexing
摘要： The idea of this paper is to utilize the advantages of the optical fibers over conventional wiring methods in order to construct a system for transmitting analog stereo audio signal. The main goal is to create a low-cost analog stereo audio transmitting system using one optical fiber, with sophisticated sound quality. The system was built for transmitting an analog audio signals over plastic optical fiber by applying multiplexing over wavelengths. This method enables the transmitting of two analog audio signals over a single optical fiber. As a result, the audio signal can be transmitted over long ranges and using only one transmitting medium. In comparison with coaxial wired analog audio systems, optical fiber wired analog audio system has better signal-to-noise ratio, better frequency response and wider bandwidth.
关键词： wavelength division multiplexing,plastic optical fiber,analog stereo audio signal,optical fibers,signal-to-noise ratio
更新于2025-09-23 15:19:57
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A long-wavelength-emitting fluorescent probe for simultaneous discrimination of H2S/Cys/GSH and its bio-imaging applications
摘要： A long-wavelength fluorescent probe NR-CY was developed for simultaneous identification of cysteine / glutathione and sulphide by combining the derivative of Nile red with 7-nitrobenzofurazan. The response of NR-CY to thiols is regulated by intramolecular charge transfer and photoinduced electron transfer mechanisms. For sulphide at 560 nm, cysteine at 475 nm and glutathione at 425 nm, different absorbance increases can be observed. NR-CY can detect cysteine at fluorescence emission 543 nm and distinguish sulphide from other analytes by kinetic experiments at 636 nm. The probe showed a rapid response to these thiols (cysteine was 90 s and sulphide was 30 s). In addition, NR-CY has been successfully applied to live MCF-7 cell imaging.
关键词： biothiols,Fluorescent probe,cell imaging,long-wavelength-emitting
更新于2025-09-23 15:19:57
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[IEEE 2018 IEEE CPMT Symposium Japan (ICSJ) - Kyoto, Japan (2018.11.19-2018.11.21)] 2018 IEEE CPMT Symposium Japan (ICSJ) - Wavelength matching of resonance reflection and guided-wave launching for high-performance CRIGF
摘要： Cavity-resonator-integrated guided-mode resonance filter is investigated for an external mirror of laser and a waveguide coupler. Matching wavelengths giving the maximum reflectance and the maximum coupling is theoretically and experimentally investigated.
关键词： Wavelength selective reflectors,Guided-mode resonance,Multi-wavelength light sources
更新于2025-09-19 17:15:36